A bipartisan group of 20 senators on Tuesday implored former colleague John Kerry to ensure the State Department approves the proposed Keystone XL pipeline by April.

In a letter to Kerry, the newly installed secretary of state, the senators insisted that the Obama administration should keep to its earlier announced timetable for deciding whether the $7 billion project is in the “national interest.”

Pipeline advocates fret that the final decision could stretch long beyond the end of the first quarter, when the State Department previously predicted it would be done reviewing the project.

“As you begin your tenure as secretary of state, we urge you to make the timely approval of the Keystone XL pipeline one of your top priorities,” the senators wrote. “We believe that you and the president should remain committed to reaching a decision within the first quarter of this year.”

The letter was spearheaded by Sens. John Hoeven, R-N.D., and Max Baucus, D-Mont., whose states are hotbeds of tight oil drilling that could benefit by using the pipeline to transport crude south, well beyond a bottleneck in Cushing, Okla.

The Obama administration rejected a permit for the northern leg of the project last year, saying a planned rerouting in Nebraska required more environmental study. Nebraska approved the new path in January.

A southern stretch through Oklahoma and Texas, already under construction, doesn't require the State Department OK because it doesn't cross an international border.

Environmentalists say the pipeline would expand the marketplace for bitumen harvested from the oil sands through mining or steam-based approaches that are more energy-intensive than conventional crude production.

Pipeline advocates reject opponents' assertions that diluted bitumen from Canada is significantly dirtier than the crudes from Venezuela and other nations that it likely would displace in Gulf Coast refineries.